As far as using this field for svn repos, I assume that it should be to
an anonymous-friendly version of the repo if possible (svn:// not
svn+ssh://). Should it link to the trunk, rather than the head of the
repo? I think so and that's how your example gives it.
As to it being an XS- field, dpkg-dev doesn't warn at all about building
packages with such a field (unlike an XB- field), so I don't really
care, although it seems it would be better to lose the XS- if possible.
Very good idea on this, I'll be adding it to all my packages, and to all
of d-i, if someone else doesn't do it first.
Have you thought at all about automated systems that could be built on
top of this? Things like a repo browser that can browse (and find recent
changes in) all packages, or mirrors of repos that arn't hosted at
svn.debian.org, or what have you.
--
see shy jo